An example of such a system is a clock thermostat for controlling the central heating. Such a system enables a user to program the temperature in the course of the day. For this purpose, a user typically has to enter a number of clock times and for each clock time the desired temperature. Alternatively, the clock thermostat provides for a limited number of continuously adjustable temperature values, e.g. night and day temperatures, and each user-supplied clock time is related to any of these temperature values.
Another example of a system defined in the opening paragraph is an alarm clock, which can be programmed to produce an auditory wake-up signal, which may be a buzz or a radio program. Such an alarm clock also enables the user to enter one or a few clock times at which the wake-up signal has to be produced.
A disadvantage of the known systems is that the programming is cumbersome, requires a lot of button presses in a very precise order, offers limited programming options, is difficult to learn and easy to forget.